Existing indoor outdoor two temperature control systems designed for use on hydronic boilers provide an automatically adjusted temperature set point based on outdoor temperature and hydronic boiler temperature. As the outdoor temperature drops the hydronic boiler temperature set point is raised. As the outside gets warmer the hydronic boiler temperature set point is lowered. In some installations the hydronic boiler is automatically switched off when the outside temperature reaches a pre-set temperature. The hydronic boiler is automatically switched back on when the outside temperature drops below the pre-set temperature.
The two temperature indoor-outdoor control system cannot anticipate changes in outdoor weather conditions and therefore cannot react in advance to sudden increases in outdoor temperature, resulting in overheating and wasted energy.